Homogenization of 7075 and 7049 Aluminium Alloys Intended for Extrusion Welding

Round 1

Reviewer 1 Report

The effect of processing parameters on homogenization of Al-Zn-Mg-Cu alloys was investigated. These materials are intended for extrusion welding. However, in this paper, nothing about extrusion welding can be found. How to prove that the homogenized alloy is suitable for extrusion welding. The reviewer believes that the content of this article completely deviates from the subject. REJECT is suggested.

 

Author Response

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Reviewer 2 Report

This paper uses a combination of DSC and SEM/EDS to investigate the homogenisation response of four 7xxx-series AL alloys. DSC is used to characterise the incipient melting and solidus temperature and enthalpy and SEM/EDS is used to characterise the coarse constituents in a range of conditions. The paper is well presented and organised in a logical manner. Apart from very minor mistakes pointing out below, I am satisfied that this paper is ready for publication in the Metals journal.

In general, the authors could expand their reference list. There is a wide body of literature on this subject. More comparison to literature should also be provided in the discussion.

Line 364, the authors mention “in many papers” with no references mentioned. Would you please be able to add appropriate references

“depended on” in the abstract should be “dependent on”

Line 132 “hating rate”

Line 328 “lover” instead of “lower”

Line 353 “In a result,” is used a couple of times when the authors mean “As a result”

Author Response

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Reviewer 3 Report

Paper Metals- 1034294                                                                      17 January, 2021

This research is of great interest, focused in extrusion processes which use porthole dies, where a good solid state joint/weld in the extrusion die must take place before the final (hollow) extrusion profile is obtained. The work is well justified and should be of undoubtable attention from an industrial point of view, and therefore, worth publishing.

However…

The paper cannot be accepted the way it is now presented. It lacks of a number of flaws which the authors should address before it can be accepted for publication.

The paper is very hard to follow. It contains a lot of results, which connection among them and with the final objective of the paper, difficult to track. Four Al alloys (with different amount of mainly Zn, Mg, Cu elements, 7xxx series) are investigated.  There are three 7075 alloys and another 7049, with more Zn than the 7075 alloys. Why this selection? Which criterion has been assumed to select the three 7075 alloys? To what extent has the amount of alloying elements been controlled when manufacturing the alloys?

The introductory section is too extensive and confusing… and so are the Results and Discussion ones. The number of figures is, by far, too high. The paper contains 18 figures, many of them subdivided into several ones… Figure 4 displays four micrographs of the as cast alloys … but all look similar.   figure 8 contains five plots … but they are not even commented in the text..  figure 9 contains seven sub-figures …

As far as I have understood, the idea of this paper is to increase solidus temperature in 7xxx to increase extrusion temperature a facilitate welding of the alloys within the porthole dies by homogenization treatments. However, a lot of distracting arguments around the microstructure evolution from microscopic and DSC experiments are presented. This does not help in a constructive discussion.

I would suggest the authors to reduce the length of the paper as well as the number of figures. There are a total of 30 micrographs, 28 plots, and 15 tables (!!). This is not acceptable, by any means, for a journal regular paper … Include only those which are really relevant for the (interesting) objective of the work, and reduce (radically) the text. Try not to subdivide figures into several ones, as this distracts the reader from the main stream of the paper. For example, the homogenization treatments described in the three plots of figure 1 can be included into one single plot. Avoid speculative and unnecessary descriptions of microstructural changes, regardless they may be of interest... but in another context.

Be systematic in the description of results. There are many alloys and many homogenization treatments … Jumping from one alloy-treatment to another alloy-treatment is confusing.

The concept “low melting microstructure components” referred to throughout the paper several times, is confusing… do you mean precipitates or second phase particles? Please, use conventional terms…

The English is OK. The paper is, in general, well written, though some sentences are confusing (e.g., lines 211, 212). I would advise the revision of the text by a native English speaker once a new final version of this work is completed.

Line 131 In all cases,

Line 132 heating

Author Response

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Round 2

Reviewer 1 Report

The authors have made partly responses to the comments. The modifications are satisfied to some extent.

Author Response

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Reviewer 3 Report

Most of the comments raised in my previous report have been properly addressed and the document has been greatly improved. But the document still needs to shorten the Introduction and Discussion sections. They are the same length as in the first version of the article. It is mandatory that the authors carry out, in particular in the introduction, a synthesis exercise to facilitate to the readers the importance of the research and the analysis of the results carried out.

Author Response

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Round 3

Reviewer 3 Report

After final corrections, the paper is now ready to be publised.

Thank you.